Resistor structure with adjustably positionable taps



NOV. 25, 1952 Z T K 2,619,570

RESISTOR STRUCTURE WITH ADJUSTABLY POSITIONABLE TAPS Filed May 27, 1952 \III INVENTOR. ZoZiczn TczifaZS Patented Nov. 25, 1952 :RESISTOR STRUCTURE ..WITH- ADJ USTABLY- IOSITIONABLE TAPS Zoltan Taka'ts, Vestal, N. Y., assignorto Dejur- Amsco Corporation, Long'Island City, N.'Y., a

corporation of New York Application May 27, 1952, Serial No. 290,114

6 Claims. 1

The "present invention relates *to' a resistor structure and to the structure ofa cooperating adjustable tapcontact,'.by means of which accurate positioning of the tap with respect-to the resistor is .facilitated with the use solelyof unmodified standardized equipment.

In units embodying potentiometers and fixed or variable resistors, it isoften desired to utilize a'portion'of the resistor toform aresistance of predetermined magnitude. The employment of contacts adapted to make electrical engagement with. the resistorat appropriate points along itslength is conventional for this purpose. The .tapcontact must be very accurately located with respectto the resistor, and to, this end it has generally-beennecessary to design each unit for the particular .application in which it is to be used.. .Even in thecase of similar. units for use under thesame. conditions, unavoidable variations in theresistor itself usually render. .it necessary'that the tap. contacts. be individually positioned in eachunit if thedesired degree of accuracy is-tobe attained. This is, of course, an extremely timeconsuming task and, moreover, has in the pastrequired the employmenteof units which must be individually modifiedfor the particular application-involved and even for the purpose of compensating for the. variations inherent in fabrication of the resistor.

The present invention has asits prime object the production of;.-a unitincluding afixedresistor .with'which tap contacts may be-electrically engaged at any-point along its length, the unit itself and the structureof the-tap contacts being so cooperatively designed that standard units and contacts may be employed for all values of .tapped resistance,- and so that the accurate positioning of the tappedcontactsavith respectto theresistor may bereadily accomplishedon a production basis.

this way a single standard resistor or potentiometer unit may. be produced for all applications, thus materially decreasing the cost of such units. The same units may be'used with or without tap contacts, and the tap contacts, maybe applied thereto and adjusted thereon in such a simple. manner'that the necessary connections maybe made in the IfiGld, and units originally purchased for use withouttaps can havertaps readily applied thereto even by semi-skilled personnel.

When taps are employed to producea plurality of fixedresistances of closely similar values, the tap contacts must electrically engage the resistor at closelyadjacent points. In ordergto permit this to be accomplished in a simple manner, standard tap contacts of special shape havebeen "designed.

In order to provide for the above described ready adjustability of the tap contacts, the resistor structure of the present invention is provided with an insulating member extending alongside and substantially parallel to the resistor and having a plurality of spaced recesses along the length thereof, these recesses being adapted to receive a fastening'element such as a screw which passes through the tap contact and secures the tap contact in place against the insulating member. Standardization of structure is attained by spacing the recesses 'fairly closely to one another and by providing the body of the tap contact with an elongated aperture through which thefastening element passes, the length of that aperture being suflicientto encompass two adiacent recesses in theinsulating member together with space between those recesses. In this way, no matter where the tap contact may have to be positioned relative to the resistor, the aperture in its body portion will expose at least one recess into which the-fastening element may enter.

In order to permit tapping of the resistor at points closely adjacent to one another, a tap contact may be employed in which the resistorengaging finger not only extends from the body of the contact toward the resistor but also has a: lateral extension'projecting in the direction of the length of the resistor, the tip of the extension being adapted to engage the resistor. Such a tap contact can be mounted on the insulatingtmember at a'point remote'from the previously positioned tap contacts, but electrical engagement with the resistor will still be accomplished at a point close to the point. of electrical engagement of the previously positioned contacts.

To the accomplishment of the above, and to such other objects as may hereinafter appear,

sembled and the right hand side of Fig. 2.show- 6 ing a modified construction in which all of the inner parts are integral;

Fig. 3 is a view similar to Fig. l but with the rotor in place;

Fig. 4 is a perspective view of one type of standard tap contact; and

Fig. 5 is a perspective view of another type of tap contact.

Since the invention is particularly well adapted to be incorporated into a variable resistor or potentiometer structure, it is here thus illustrated, that structure comprising a casing defined by a bottom wall 2 and a side wall 4, the bottom wall having an aperture 6 through which the shaft 8 carrying the rotor assembly I8 is rotatably received. The resistor I2 is defined by an extended length of resistor wire l4 wound helically about a fiat supporting sheet l6 of insulating material, that sheet being bent around the interior of the casing side wall 4, being separated therefrom by means of an insulating sheet l8 and separated from the bottom wall 2 by an insulating disc l8, and secured in place in any appropriate manner so that the ends 28 and 22 of the resistor are separated. Appropriate electrical connections are made between the ends 28 and 22 and selected terminal pins 24 mounted on the outside of the casing.

The rotor assembly 18 carries a conductive contact arrangement including a finger 26 adapted to slide along the resistor 12 and a pair of fingers 28 conductively connected to the fingers '26 and riding over collector ring 38, the latter being provided with a terminal tab 82, the wire 34 making electrical connection between the tab 32 and another of the terminal pins 24.

Having reference to the left hand side of Fig. 2, the collector ring 38 is mounted on an insulating ring 36 which may in turn be closely fitted around a metallic bushing 38 defining a hearing for the shaft 8. As shown in the right hand side of Fig. 2, the ring 36 and the bushing 38 may be integrally formed of some suitable hard insulating material such as nylon, this being designated by the reference numeral 48, thus simultaneously providing a bearing for the shaft 8 and an insulated mounting for the collector ring 38. The rotor assembly 18 is generally insulated from the shaft by means of an insulating washer '42, the rotor assembly being clamped about that washer by means of screw 44.

In order to provide for mounting of the tap contacts, another insulating ring 46 is mounted on the bottom wall 2 outside the ring 36 but inside and spaced from the resistor 12. In the left hand side of Fig. 2 the ring 46 is shown as a separate element, but, as shown in the right side of Fig. 2 and designated by the reference numeral 46, it could also be formed integral with the part 46. As may best be seen from Figs. 1 and 3, that portion of the ring 46 which extends alongside the resistor I2 is provided with a plurality of recesses 48 equally spaced along the efiective length of the ring 46.

One form of standard tap contact specifically efiective length, at least one recess 48 will be completely exposed through the aperture 54. A screw or other fastening element 56 is adapted to pass through the slot 54 and into an appropriate recess 48, engagement between the fastening element 56 and the recess 48 clamping the contact body portion 52 in place on the ring 46. As here specifically disclosed the recesses 48 are in the form of tapped holes and the fastening elements 56 are in the form of screws, the screws 56 being screwed into the holes 48 and the screw heads having lock washers 58 interposed between themselves and the body portion 52.

The contact 58 is provided with a finger 68 extending from one end of the body portion 52 toward and into engagement with the exposed wire I 4 of the resistor l2, that finger 68 being generally of U-shape so as to first project downwardly from the body portion 52 toward the bottom casing wall 2, then along the bottom casing wall toward the resistor l2, and then upwardly into engagement with the resistor. The U-shape of the finger 68 not only provides a desired degree of resiliency in that finger, thus ensuring proper electrical contact with the resistor [2, but also helps to fix the position of the contact body portion 52 on the upper surface of the ring 46. The contact 58 is provided with another finger 6'2 projecting from the opposite end of the body portion 52 but in the same general direction as the finger 68, the finger 62 having an .L-shape, first extending downwardly from the body portion 52 toward the bottom casing wall 2, and then extending parallel to the bottom casing wall 2 to a point short of the resistor l2, the tip of the finger 62 being provided with an aperture 64 for reception of a suitable conductive wire (not shown) by means of which electrical connection may be made between a selected terminal pin 24 and that point on the resistor I2. which is engaged by the tip of finger 68 of the tap contact 58, said finger tip being provided with a protrusion 66 to facilitate precise electrical engagement.

It will be appreciated that because of the length of the aperture 54 with respect to the size and spacing of the recesses 48 thecontact 58 may be clamped to the ring 46 at any desired position along its efiective length. In practice it would first be approximately positioned and the screw 55 would be passed through the aperture 54 into an appropriate recess 48 but the screw 56 would not be screwed all the way down. The position of the contact 58 would then be adjusted, as permitted by the elongated slot 54, until direct electrical measurement indicated that its finger 68 was engaging the resistor I2 at precisely the proper point, and the screw 56 would then be screwed down into the tapped hole 48 so as to lock the contact 58 in place along the ring 46, thus in turn fixing the position of engagement between the finger 68 and the resistor l2.

If it is desired to tap the resistor l2 at a second point closely adjacent to the point at which the finger 68 of the contact 58 engages that resistor, a second contact 58 may be employed which is closely similar to the contact 58 except that the fingers 68 and 62' extend from opposite sides of the body portion 52 when compared with the fingers 68 and 62 of the contact 58. This expedient is adopted in order to avoid inadmissible overlapping of the body portions 52 of adjacent contacts.

When still a third tap is desired at a point closely adjacent to the tapped points previously achieved (by closely adjacent, here and above, is meant separated by a distance less than the length of the contact body portion 52), a third type of contact is employed designated by the reference numeral 50" and shown in Fig. 5. This contact is similar either to the contacts 56 or 50 except for the fact that the upwardly extending portion of the finger 60" of the contact 50" does not itself engage the resistor 12 but instead has a lateral extension 68 projecting in the direction of the length of the resistor I2 and inclining toward that resistor, the tip of the lateral extension 68 being provided with a projection 66" for engagement with the resistor I2. Hence, as may be seen from an examination of Figs. 1 and 2, by the use of the contacts 50, 50' and 5D", the resistor I2 is tapped at three points all closely spaced from one another, and each of the contacts may be individually adjusted so that any desired magnitude of resistance can be achieved.

The significant fact is that the resistor [2 may be tapped at a plurality of points having any desired spacing relative to one another through the use of standardized and uniform parts. The unit without the tap contacts is a conventional potentiometer or variable resistor unit and may be sold as such to those customers who do not desire or need taps. The very same unit may be used without any modification where taps are required, the unit being constructed so that the taps may be applied thereto at any time and in any position. Standardized inexpensive tap contacts may be employed, and may be placed in proper position even by semi-skilled labor. The resultant savings in initial cost and in labor incident to adaptation to special installations are obvious.

While but one embodiment of the present invention has been here disclosed, it will be apparent that many variations may be made in the details thereof, all within the spirit of the invention as defined in the following claims.

I claim:

1. In a resistor structure, a casing, a resistor extending inside said casing, an insulating member secured to said casing and extending substantially alongside said resistor and having a plurality of spaced recesses therein extending in a line substantially parallel to said resistor, and an adjustable tap contact secured to said member by a fastenin element receivable in one of said recesses, said contact comprising a body receivable over that portion of said insulating member having said line of recesses, said body having an elongated aperture through which said screw is adapted to pass, the length of said aperture being at least equal to the distance between remote edges of adjacent recesses, and a finger extending from said body toward and into engagement with said resistor.

2. The resistor of claim 1, in which said finger extends from said body adjacent to one end thereof, and in which another finger extends from said body adjacent the other end thereof, said other finger being shaped so as to avoid engagement with said resistor and serving as a terminal tab.

3. The resistor of claim 1, in which said finger extends from said body toward but short of said resistor, and includes an extension projecting substantially in the direction of the length of said resistor and inclined toward said resistor so as to engage therewith at a point spaced from said contact body along the length thereof.

4. In a resistor, a casing having a bottom wall and a side Wall, a resistor extending around said casing inside said side wall, an insulating ring secured to and extending up from said bottom wall concentrically with and radially spaced from said resistor, the upper surface of said ring having a plurality of equally spaced tapped holes therein, and an adjustable tap contact secured to said ring by a screw engageable in one of said tapped holes, said contact comprising a body receivable on the upper surface of said ring and having an elongated aperture therethrough through which said screw is adapted to pass, the length of said aperture being at least equal to the distance between remote edges of adjacent holes, and a U-shaped finger extending from said body downwardly toward said bottom wall, along said bottom wall toward said resistor, and upwardly into engagement with said resistor.

5. The resistor of claim 4, in which said finger extends from said body adjacent one end thereof, and in which another finger extends from said body downwardly toward said bottom wall and along said bottom wall toward but short of said resistor, said other finger serving as a terminal tab.

6. The resistor of claim 4, in which the upwardly extending portion of said finger does not engage said resistor and has a lateral extension projecting therefrom substantially in the direction of the length of said resistor and inclined toward said resistor so as to engage therewith at a point spaced from said contact body along the length thereof.

ZOLTAN TAKATS.

No references cited. 

